1. Field of the Invention
The field of the present invention relates generally to an apparatus and method for determining viscoeleastic properties of mammalian cervical mucous. For humans, the determination of the viscoelastic properties of the mucous can be used to predict and indicate inception and presence of ovulation for increasing the likelihood of conception or for contraception. For livestock and other mammals, the determination can be used to detect estrus for breeding management.
2. Description of the Prior Art
Many forms of family planning require a woman wanting to avoid pregnancy to identify her fertile period so she can practice sexual abstinence or use other means or birth control during this period. On the other hand, many marginally fertile couples desiring pregnancy have a higher probability of conceiving if sexual intercourse is confined to the woman's fertile period or if the capsules abstain for several days before the period. Ovulation is the key event in the female fertile period. The fertile period for women typically consists of only about four days in the menstrual cycle: three days preceding ovulation (necessitated by sperm survival), and one day after ovulation (necessitated by ovum survival).
It is well known that the rheology of cervical mucous undergoes significant changes at the onset and throughout the female fertile period. See Schuster, U.S. Pat. No. 3,982,423 (1976). During the immediate pre-ovulatory phase and the rest of the menstrual cycle, the mucous becomes less abundant and no longer possesses certain threadability characteristics. In rheological terms, the muscous is highly viscous except during the ovulation phase of the menstrual cycle. If one can determine the changes in the viscoelastic properties of cervical mucous that occur before the onset of ovulation, it is possible to pinpoint the female fertile period.
Accordingly, there exists a need for a simple, accurate and easy-to-use device which women can use in the comfort and privacy of their own home to identify their fertile period to either increase the likelihood of conception or to practice birth control by either sextual abstinence or another form of birth control.
In the so-called Billings method of contraception by periodic abstinence, a woman is taught to identify the precise characteristics of cervical mucous produced at various states of her menstrual cycle and their relationship to her fertile and infertile days. The method tends to be subjective and lacks quantitative precision so it tends to be unreliable. The more widely practiced Basal body temperature method uses the changes in daily temperature taken immediately at awakening to identify the temperature shift that occurs at or shortly after ovulation. To be effective, the woman must adhere to a highly repetitive routine before the daily temperature taking because any restlessness, motion, infection or mental stress causes small temperature shifts, which can result in incorrect data. The Sympto-Therman method charts temperature changes and changes in volume and viscosity of cervical muscous and teaches women to recognize such subjective symptoms of ovulation as intermenstrual pain. This method fares no better because the measurements lack precision and objectivity.
Kopito, U.S. Pat. No. 3,979,946 (1976) and the aforementioned Schuster patent both teach devices designed to give quantitative measurements of rheological properties of cervical mucous, including its viscoelastic properties, but both are complex and difficult to use and are mechanical devices subject to error. In addition, the mucous is not tested in vivo. Thus, such devices are not suitable for widespread use by women in the comfort and privacy of their own home.
In addition to the needs of women and couples who wish to identify the inception and presence of ovulation in the human female, the detection of the inception and presence of ovulation in other mammals is also important for the purpose of breeding. Thus, for example, detecting estrus in cattle is important, but also difficult, for the farmer. Failure to detect estrus at the proper time means delayed breeding and long calving intervals, which result in a decreased production of milk and beef. The problem is further complicated as herd size increases because it is difficult to observe more cows. Various techniques have been advanced for the detection of estrus in cattle. For example, Scott, U.S. Pat. No. 4,224,949 (1980), and McDougall, U.S. Pat. No. 3,844,276 (1974), test electrical resistance of cervical mucous using a bovine vaginal probe. Rodian, U.S. Pat. No. 4,247,758 (1981), measures movements of animals which are said to be increased during estrus. Zartman, U.S. Pat. No. 4,387,724 (1983), measures long-term deep body temperature. However, none of these techniques utilizes changes in rheological parameters such as viscosity for bovine cervical mucous at the onset and throughout the bovine estrus period. Thus, there exists a need for a simple and quick apparatus and method for accurately detecting the inception and presence of ovulation in mammals, such as cattle, which are bred.